Grammar studies the structure of words, the ways in which they are linked and the meanings to which such combinations give rise to
The spelling of a language is the set of rules that govern it to be spelled correctly. Spelling, in a nutshell, is the normative part of language.
Therefore the sentence is grammatically correct but has a spelling error when writing the word "chuchillo" where the correct word is "cuchillo" which means knife.
Chica is feminine... reservada is feminine... so which of your options are feminine? Ella and la. Ella means she so it can't work, as that would mean she girl is very reserved. La is the femenine the. So that is your answer.
